Line voltage monitors have come into widespread use over the last ten or fifteen years. However the detectors presently in use are expensive and have severe disadvantages. Not the least of the disadvantages is that the monitors comprise a detector and a printer and a data entry device. Some monitors according to the prior are utilize switches of various kinds for entering a limited number of thresholds. Others provide a full numeric keyboard and ON-LINE display such as LED's. Furthermore, these prior art devices do not detect and store events of many of the qualities and numbers that are desired by the users.